docs: def clean(self):
          '''
          Only allow submission if there are not already slots in the submitted window,
          and only allow rooms associated with the chosen location.
          '''
  
          super(SlotCreationForm,self).clean()
  
          startDate = self.cleaned_data.get('startDate')
          endDate = self.cleaned_data.get('endDate')
          startTime = self.cleaned_data.get('startTime')
          endTime = self.cleaned_data.get('endTime')
          instructor = self.cleaned_data.get('instructorId')
  
          existingSlots = InstructorAvailabilitySlot.objects.filter(
              instructor=instructor,
              startTime__gt=(
                  ensure_localtime(datetime.combine(startDate,startTime)) -
                  timedelta(minutes=getConstant('privateLessons__lessonLengthInterval'))
              ),
              startTime__lt=ensure_localtime(datetime.combine(endDate,endTime)),
          )
  
          if existingSlots.exists():
              raise ValidationError(_('Newly created slots cannot overlap existing slots for this instructor.'),code='invalid')